1. Field of the Invention
The present invention relates to a recording apparatus which prints an ink picture by depositing a fluid ink by means of flying or contacting on a recording medium such as paper or the like according to input signal information such as picture of the like.
2. Prior Arts
As method of picture recording on a plain paper, several methods have been proposed. Among such proposed methods, ink-jet method and magnetic fluid ink method are known as practical methods.
The ink-jet method has several types therein, but the fundamental principle thereof is that fluid ink is spouted from a nozzle having a very fine hole on a plain paper. Among the ink-jet method, a method called ink-on-demand type (disclosed by E. Stemme et al in IEEE Transactions on Electron Devices vol. ED-20 p14), which modulates amount of the spouted ink corresponding to input picture signal by utilizing electric vibration of a piezoelectric device, is attracting an attention, since it can easily carry out a high speed recording.
On the other hand, magnetic ink recording method has several types, and among them a method called as magnetic ink flying recording (disclosed by Yoichi Sekine et al in the Japanese unexamined Patent publication No. SHO54-23534), which makes fluid magnetic ink to become protruded by means of magnetic force, is attracting attention in simplicity and high resolution.
The above-mentioned ink-jet method has a defect which is substantially difficult to eliminate. That is, the nozzle with a fine hole is likely to be choked with dried ink which makes the operation impossible. This is the most important and difficult point to improve.
The above-mentioned magnetic ink flying method requires an inclusion of magnetic fine powder of, for instance, magnetite or .gamma.-ferrite. This magnetic powder is likely to cause chemical change due to oxidation and etc, and makes the record change from black color to brownish black color. Besides, color of the magnetic ink is limited and therefore range of color selection of the ink is narrow; especially, to produce inks of high color purities of cyan, magenta and yellow have been very difficult, and therefore, color printing by the magnetic ink method has been technically difficult.
From the abovementioned standpoint, the present inventor previously proposed a recording apparatus employing an ink printing head having substantially a needle-shaped recording electrode, an auxiliary electrode so installed as to surround the abovementioned needle-shaped recording electrode on a perpendicular plane to above-mentioned recording electrode, and a dielectric substance substrate so disposed as to connect between the above-mentioned both electrodes.
The abovementioned head is a recording head which forms a protrusion of fluid ink by means of electroosmotic travelling of fluid ink for a dielectric substance and its principle is that this protruded fluid ink is caused to fly and deposit onto a recording medium by means of coulomb force to record and reproduce an ink picture on a recording medium corresponding to picture signal. (Japan Patent Application Sho 55-113887 of Aug. 18, 1980).
In the abovementioned apparatus, a needle-shaped recording electrode is installed on one surface of a sheet-shaped dielectric substance substrate facing a recording medium, and the recording electrode is disposed close to the recording medium, having an exposed conductive end tip part, and an auxiliary electrode surrounding this recording electrode is installed on the dielectric substance substrate surface on which the fluid ink is disposed, and a voltage is applied across the recording electrode and the auxiliary electrode.
In this apparatus, a protrusion of ink is formed on the abovementioned exposed conductive end part surface by electroosmotic travelling of fluid ink, and a high voltage is applied across the recording electrode and the recording medium, thereby the ink is caused to fly onto the recording medium by means of this coulomb force.
However, in such a configuration that the end tip part of recording electrode and the auxiliary electrode are formed on the same surface in an exposed fashion, three-dimensional wiring is required to supply voltage between this end tip part and the auxiliary electrode while insulating them each other, or an electric insulation of the auxiliary electrode against the fluid ink is required to prevent any unnecessary ink protrusion other than the abovementioned exposed end tip part. These drawbacks are liable to cause an operational instability and often makes a high resolution of recording difficult because of production engineering problems.
Furthermore, the average ink recording requires a passing-through installation of high density as many as 8 lines/mm in the abovementioned structure, but this includes a problem of difficult production engineering because the recording electrode is installed by passing through the dielectric substance substrate.